It is known that a compound having two or more mercapto groups [R—(SH)a, wherein R is an organic group of “a” valent such as alkylene group which can possess a branch group or arylene group] is used to synthesize the resin of high refractive index (ND20° C.≧1.60) by reacting with, for example, polyisocyanates (refer to JPS60-199016 Laid-open publication and JPS62-267316 Laid-open publication). As the related prior arts, in JPH8-269161 Laid-open publication, 2,2′-dimethylmercaptobiphenyl and 4,4′-dimercaptobiphenyl are reported as the biphenyl derivatives of dimethylmercapto compound.
And further, there is a description illustrating that the reacted components substituted with allyl group or halogen contributes to the improvement of refractive index.
Furthermore, it is known that the compounds having a thiol group can form a mono molecular film composed of above mentioned compounds on the surface of metal or on the surface of fine metal particles of metals, such as noble metal for example, Au, Pt, Ag or Pd and transition metal, in self-assembling manner by an electron force of S atom. Mono molecular film mentioned above is also converted to the film with various function by bonding a compound which imparts various function to the surface of said mono molecular film to an another end group of said compounds selected from a group consisting of thiol and other than thiol.
For example, a self assembling film is formed by using a compound with a functional group that reacts structural specifically (specifically, like as antigen-antibody reaction) and by combining said film with Quartz-Crystal Microbalance, and applying above mentioned idea e.g. for the method to detect DNA quantitatively has already proposed (Document 1; Kenichi Niikura et al. Chem. Letter 1996, 863–864).
Further, the following prior art has also proposed; which comprises (1) synthesizing PEG derivative by introducing a functional group (for example, mercapto group or polyamine group), via which the PEG derivative is loaded on the surface of ultra fine particles of metal, metal oxide or semi conductor to one end (for example, α-end) of a PEG and a functional group which can react with a functional compound such as antibody, protein or dye to another end (ω-end) of the PEG, and (2) loading the PEG derivative synthesized above on fine particles of metal, metal oxide or semi conductor to improve the dispersing stability and to posse (to be modified with) a functional group having the reactivity with a functional compound to the other end of PEG chain expanding from the surface (extends to the outer side) of fine particles to obtain a new dispersion stabilized complex [refer to Document 2; 48th Polymer forum (1999), October 6–8, at Niigata University, Igarashi Campus “Polymer Science, Abstracts” Vol. 48, No.14, 4113–4114, issued on Sep. 20, 1999].
The reactivity and function of above mentioned mercapto group indicates one of the importance aspects of the mercapto compound. The various functions of the mercapto group are further important, because functions of a compound can be enhanced by being converted to a polymercapto compound with higher mercapto group content.
In general, the circuit in which fine semi-conductor elements are assembled is prepared by printing a pattern of circuit on a silicon substrate and to produce the circuit corresponding to the printed pattern, namely, photolithographical technique is applied. With the advancement in technique, the circuit pattern becomes fine and the line which composes the circuit pattern also becomes fine, and it is necessary for the printing means based on the photolithographical technique to use shorter wavelength.
However, for the manufacturing the molecular scale transistor, it is said that the photolithographical technique can not apply no longer. Therefore, it is required for molecular scale transistor material to have the function to coordinate in self-assembling manner to a metal electrode with the electronics characteristic.
Recently, the technique to prepare a mono molecular electronics device is proposed. The technique described above comprise (1) employing a mono molecular which possesses groups which have bonding ability with an electrode, such as SH groups on ends and field-effect semi-conductor part, donor part, acceptor part, electric conductive part and insulating part in the monomolecular, (2) and assembled the monomolecular to each electrode by end SH groups depicted above to obtain a monomolecular electronic device [Document 5; U.S. Pat. No. 6,339,227 B1 publication (patented on Jan. 15, 2002)].
Further, for example, as OH group of 3,3′4,4′-tetrahydroxybiphenyl or 2,2′,4,4′-tetrahydroxybiphenyl is used for the synthesis of polymer, the cross-linking or the function group reacting with other compound or with the group existing on the surface, so SH group has a possibility to have similar function. Therefore, each of SR groups of tetramercaptobiphenyl and the derivative thereof, and each of thiols or thiolates of tri- or tetra-thiols or thiolates of terphenyl or terphenyl derivative can respectively take part in various reactions, and it is obvious that the function of said compound can be improved along with the increase of the number of functional groups.
While, as the process for preparing an aromatic thiol, the process using a reaction of reducing an aromatic sulfochloride is most popular, and in reaction mentioned above, the combination of zinc dust and sulfuric acid (carried out at 0° C.), tin and hydrochloric acid, mixture of phosphorus, potassium iodide and phosphoric acid and lithium aluminium hydride can be used.
An object of the present invention is to provide a novel compound which has mercapto groups with more improved function depicted above. Further, to improve the variety of function of above mentioned compound, the skeletal structure to which thiols or thiolates are changed to terphenyl or terphenyl derivative and introducing three or more thiols or thiolates to the terphenyl or terphenyl derivative.
Therefore, it is important to find out a process to prepare the compound depicted above. The inventors of the present invention have found out the following methods for introducing said group with sulfur to an aromatic ring of biphenyl, terphenyl or derivatives thereof. That is,    A. a method comprising (1) synthesizing 4,4′-biphenyldisulfonylchloride or 4,4′-terphenyldisulfonylchloride by reacting ClSO3H with biphenyl or terphenyl, and (2) synthesizing di-thiol or thiolate by reacting lithium aluminium hydride with the product obtained by (1),    B. a method comprising (1) synthesizing 4,4′-biphenyldisulfonylchloride according to the process (1) mentioned above in A, (2) synthesizing 4,4′-bis(N,N′-dimethylaminosulfonyl)-biphenyl by reacting dimethylamine (HNMe2) with product obtained in (1), (3) synthesizing 4,4′-bis(N,N′-dimethylaminosulfonyl)-3,3′-dimethylcaptobiphenyl by reacting normalbutyllithium (n-BuLi) with the product obtained in (2), and further reacting simple substance of sulfur S8 with the product obtained in former reaction, (4) synthesizing (2,2-dimethyl[3,4-d]-1,3,2-dithiastanolo) biphenyl by reacting LiAlH4/NaBH4 with product obtained in (3), and finally (5) synthesizing by introducing SH groups onto 3,3′,4 and 4′ carbon in biphenyl by reacting hydrogen chloride with product obtained in (3).    C. a method comprising (1) synthesizing 4,4′-biphenyldisulfonylchloride according to the process (1) mentioned above in A, (2) synthesizing 4,4″-bis(N,N′-dimethylaminosulfonyl)-terphenyl by reacting dimethylamine (HNMe2) with product obtained in (1). (3) synthesizing 4,4′-bis(N,N′-dimethylaminosulfonyl)-3 and/or 3″-mercapto or dimethylmercaptoterphenyl by reacting normalbutyllithium (n-BuLi), and further reacting with simple substance of sulfur S8 with product obtained in (2), and finally (4) synthesizing 3,3″,4-trimercapto-1,1′:4′,1″-terphenyl, 3,3″,4,4″-tetramercapto-1,1′:4′,1″-terphenyl or derivatives thereof by lithiumammoniumhydrate with product obtained in (3).
And the inventors of the present invention accomplished the object mentioned above.
The object of the present invention is to provide a novel tri- or tetrathiol or thiolate of biphenyltetrathiol and biphenyltetrathiol derivatives, or a novel tri- or tetrathiol or thiolate of terphenyl or terphenyl derivatives which can improve the variety of said tetrathiol or thiolate compound. By selecting terphenyl as skeletal structure to which thiols or thiolates are attached, the variety of molecular designed can be improved, for example, the length of electric conductive molecule becomes long and the number of carbon atoms to which a substituent can be introduced is increased. Then, possibilities of development of a functional material to be applied to various fields can be expected. The improvement of the length of chain with electro conductivity brings the abundance of mono molecule device mentioned above. And considering the development of a molecular scale device, the possibility of developing a novel device with triply terminals material can be expected by functionally assembling the present compounds between metal electrodes by coordinate bond. This element makes the application to a communication device or to an electronic device possible. Further, the possibility of the application to a rubber industry, an adhesive, a paints and so on, by using chemical characteristics of SH, becomes higher.
Especially, among the compounds of the present invention, the compound having 3 or 4 substituents of thiol or thiolate has not been reported yet except of the proposal by the inventors of the present invention. The introduction of 3 or 4 substituents of thiol groups means to introduce two thiol groups selectively to the adjacent sites each other, and so the development of the technique producing said compound was not easy.